Waterboarding is torture. In the past, the US prosecuted and convicted Japanese officials who waterboarded US and allied prisoners. US Attorney General Eric Holder has unequivocally stated that waterboarding is torture.

The United States is under an absolute obligation under the Convention Against Torture (CAT) to investigate, prosecute and punish torturers. And yet, here was the former president of the United States admitting he authorised torture. And nothing.

The raison d'etre of the Convention Against Torture is to eradicate torture. And one of the primary tools for preventing torture is to prosecute and punish those who are found to have tortured. In failing to prosecute – or even investigate – George W Bush following his admission, the United States failed to uphold its obligations under CAT.

Switzerland, at least for the time being, will not be called upon to examine the regime that governed detentions at Guantánamo, the redefinition of torture that allowed for interrogation techniques that could constitute torture, and the use of stress positions, manipulation of food, sleep and temperatures, forced nudity and excessive force against detainees. The Geneva prosecutor will also now not have to comb through the nearly 200-page UN report into global practices in relation to secret detention. This report examined the "black sites" established under Bush to hold detainees in CIA custody and interrogate detainees using so-called "enhanced interrogation techniques", which have been found to constitute torture or cruel, inhuman and degrading treatment.

"This regime was clearly designed to undermine human dignity and to create a sense of futility by inducing, in many cases, severe physical and mental pain and suffering, with the aim of obtaining compliance and extracting information, resulting in exhaustion, depersonalisation and dehumanisation."

George Bush himself would also have been an excellent source of evidence in support of opening an investigation for torture: Bush acknowledged on numerous occasions that he authorised and condoned the waterboarding of detainees held in US custody. In September 2006, Bush told the world that under his leadership and authority, the United States had "changed its policies" and was using an "alternative set of procedures" on persons in secret detention facilities run by the CIA outside the United States – in violation of international law. Bush had authorised the creation of the CIA secret detention programme five years earlier. Bush confirmed that he approved the use of "enhanced interrogation techniques".

The presentation of this evidence and this case must now wait for another day, and for another country to fill the impunity gap created by the refusal of the US department of justice to open an investigation in George Bush and the torture programme he authorised. There are 147 signatory states to the Convention Against Torture, and each has the obligation to open an investigation – should George Bush decide to travel to one of these countries. Bush, as a former president, enjoys no immunity from prosecution for torture.

The case against Bush for torture will not be taken up in Switzerland this week. But one day, this case will be heard.